Diverse pathogenetic factors are operant in systemic lupus erythematosus and lead to different forms of lupus nephritis. Detailed analysis of renal biopsy pathology is being conducted on specimens from patients with systemic lupus erythematosus. Biopsies are classified by standard major category of lupus nephritis, as well as scored on a semiquantitative scale for specific histologic changes which indicates the extent and severity of active inflammatory lesions and of chronic atrophic, fibrosing and sclerosing features. The patterns of immune complex deposition and lymphoid cell interaction with different segments of the nephron are being investigated by immunohistologic techniques and electron microscopy. Computer-based morphometric techniques are being developed to analyze more precisely the changes in renal pathology during the course of lupus nephritis. These approaches have facilitated the analysis of the effects of various types of immunosuppressive agents used to halt the progression of lupus nephritis and they will enhance our understanding of the pathogenesis of the kidney disease of systemic lupus erythematosus.